[Space] Multiple/Lots of Stars in one system

[scc]

I posted about this system before, but now I'm having trouble with a different part of it.

When dealing with lots of star how do you deal with Forbidden Zones? The Primary (1) has two distant companions (2 and 3) which in turn have their own distant companions (4 and 5) and star number 5 has made it's roll to have it's own companion (whose details I haven't really started working out yet and the system way still grow bigger)

So for Star 1 do I simply use the closest of it's companions (2) when determining the Forbidden Zone or do I have to worry about how close their companions could come to 1 at closest approach?